SUMMARY It is increasingly recognized that financial incentives can motivate behavior change and improve outcomes along the HIV care continuum. Under the right circumstances, financial incentives can increase the demand for HIV testing, change short-term sexual behavior, enhance linkage to care after HIV diagnosis, and promote antiretroviral therapy (ART) adherence. However, there are few studies of cash transfers' effect on adherence and/or retention among people living with HIV infection (PLHIV) in Sub-Saharan Africa, which has the greatest burden of HIV and faces persistent challenges with poverty and food insecurity. The proposed research will advance global knowledge about cash transfers for PLHIV by building on preliminary data from a study we conducted in Shinyanga, Tanzania. The study found that short-term cash transfers can improve ART adherence and retention in care among food insecure PLHIV. We will now leverage our established research program to improve and rigorously evaluate our cash transfer intervention, which is intended to offer short-term support during the vulnerable period of treatment initiation, support the development of good adherence habits, and protect individual and household welfare. In our 5-year study, we will first determine in a randomized study with 519 PLHIV whether a smaller cash transfer can improve retention in care and viral suppression at 12 months (Aim 1). After selecting the optimal cash transfer size, we will implement a cluster-randomized trial in 32 facilities with 1,984 PLHIV to evaluate the cash transfer intervention for its effectiveness on 12-month viral suppression (Aim 2). We will also conduct a mixed-methods process evaluation to understand facility-level implementation successes and challenges (Aim 3). Throughout our project, cash transfers will be delivered through an innovative and efficient mHealth system that overcomes the resource-intensive process of manually distributing cash transfers. At the conclusion of the project, we will have determined an efficient and scalable model of the intervention and its effectiveness, consistent with an implementation science approach to close the gap between evidence and practice in real-world contexts. This timely information will be widely applicable to the spectrum of cash transfer programs currently being designed, implemented, or under consideration to improve the health of PLHIV. Furthermore, this research will help policy makers understand whether cash transfers should be incorporated into ongoing `treatment as prevention' (TasP) programs.